Material forming method and apparatus



March 8, 1966 L. F. COFFIN, JR 3,238,756-

MATERIAL FORMING METHOD AND APPARATUS Filed May 3, 1961 4 Sheets-Sheet 1Inskm Pbsses I I I l l7 5 I Fbsses a. Q) Q In vemor F Louis E Coffin,Jr, 005- by 21 I I 2 J) ,6 24 3 1 77s Afro/nay- March 8, 1966 L. F.COFFIN, JR 3,233,755

MATERIAL FORMING METHOD AND APPARKTUS Filed May S, 1961 4 Sheets-Sheet.n M M H r n m c Q 8 F. M V s A m w w 0 LH 11: ua Y Q QS LN Q S March 8,1966 1.. F. COFFIN, JR

MATERIAL FORMING METHOD AND APPARATUS 4 Sheets-Sheet 5 Filed May 5, 1961tua w 233m fiol/ Farce (P Hall Fame (P f is: 2% mm mukw Ro/l Farce (PC)//7 vemor: Louis E Goff/n, Jn,

Thickness March 8, 1966 L. F. COFFIN, JR

MATERIAL FORMING METHOD AND APPARATUS 4 Sheets-Sheet 4 Filed May 5, 1961Fig. /4

Fig. /5

United States Patent 3,238,756 MATERIAL FORMING METHOD AND APPARATUSLouis F. Coflin, Jr., Schenectady, N.Y., assignor to General ElectricCompany, a corporation of New York Filed May 3, 1961, Ser. No. 108,230 5Claims. (Cl. 72-232) This application is a continuation-in-part of mycopending patent application, Serial No. 811,298, filed May 4, 1959, nowabandoned.

The present invention relates generally to the art of shaping ordeforming materials such as metals and isthickness of a metal body suchas a bar, a sheet, a strip or a thin foil. This invention is furtherconcerned with a new apparatus implementing that novel method.

The excessive cost of conventional metal working machines and equipmentsuch as mills for rolling iron and steel in thin gauges has longrepresented an important problem. Prior to the present invention,however, there has been no satisfactory answer to this problem andconsequently capital expenditure requirements have limited the use ofrolling techniques, particularly in the production of thin gaugematerial.

Over the whole gauge range of metal sheets and strips, rolling equipmentpresently in commercial use is uniformly massive and expensive andrelatively unchanged at least in basic characteristics from that whichwas standard years ago.

By virtue of the present invention, which is predicated upon mysurprising discoveries subsequently to be described, it is possibleunder certain conditions to accomplish metalworking results through theuse of rolling forces substantially smaller than those required inpresently conventional operations. This invention, therefore, opens thepossibility of extending the use of certain types of methods andapparatus and also holds the possibility of making conventional metalproducts by new techniques and machines. It additionally accords newproducts having special physical characteristics and utility.

In addition to reducing very substantially the magnitude of the rollingforces required by heretofore conventional means, this invention has theunique advantage of affording much greater control over the tolerance inwidth during thickness reduction of very wide sheet or strip stock. Theuniformity of stock thickness across the full width of the stock ismaintained automatically or inherently in accordance with thisinvention, compensating thickness reductions occurring throughout theoperation of this new method. This feature has special value and utilityin the processing of sheet or strip stock which is so hard as not to bereadily rolled for thickness reduction by prior methods.

Another novel feature and special advantage of this invention is thattension stress closely approaching the flow stress of the stock as alimit can be maintained during rolling with consistently satisfactoryresults. This contrasts with prior operations and especially tensionrolling processes in which it is necessary to limit tension stress wellbelow the optimum level to avoid excessive stock breakage.

3,238,756 Patented Mar. 8 1966 tial, tension force which, however, isless than that required to plastically stretch the metal stock in theabsence of a cyclic plastic strain, although it may approach that level,and involves repeated bending and unbending of the stock producing acyclic plastic bending strain. Such a contact-bend-stretch (CBS) rollingoperation may advantageously be carried out by running metal stockbetween and contacting it with a pair of opposed rolls which exert acontact pressure at the places where cyclic plastic strain is takingplace. This contact force is moderate at all times in the process andbecomes increasingly effective in producing elongation of the metalstock as the thickness of said stock is diminished. By comparison withheretofore conventional rolling prac tices, the pressure or forceexerted by the rolls on the stock is preferably quite small, the cyclicplastic strain again serving to magnify the effect of the contact forceto the point that plastic deformation (elongation) is produced.

This rolling operation normally will involve either running the stockrepeatedly back and forth through a processing line and therebyrepeatedly bending and unbending the stock, or running the stock oncestraight through a processing line having a plurality of roll stands. Ineither instance the stock will repeatedly be simultaneously subjected tocontact force, tension force and cyclic plastic strain and therebyelongated through successive increments of its length.

In another typical operation of this invention, rolling is conductedwhile the metal stock is under no significant tension stress, i.e., thetension force applied to the metal stock is zero or is so small as notto be a factor in the metal-working or the metal deformation process.This contact-bend rolling operation thus may be advantageously carriedout as described above, contact pressure being exerted against the stockwhere cyclic plastic strain is taking place in the stock so as topreserve the stock surface against deterioration. Here, however, theobjective of the operation may not be the elongation or the changing ofthe dimensions of the work piece, as it is in the case ofcontact-bend-stretch rolling, but instead it may be the significantalteration of the mechanical properties of the stock through the specialcombination of contact force and cyclic plastic strain. Where both newmechaniample, in an operation similar to rolling in that the sheet stockis moved lengthwise through a processing station successive portions orsegments of the length of the stock are subjected to cyclic shearingstresses which produce cyclic plastic shearing strain in the stock as ittravels in either direction through the processing line. In thisoperation, as in the contact-bend-stretch rolling operation describedabove, the sheet stock is subjected to tension constantly and is drawnout or elongated and at the same time reduced in thickness usually butnot necessarily without material reduction in its width by thecombination of the cyclic plastic shearing strain, the contact force orpressure and the tension force. Again, the contact force is somewhatless than that required to produce generally the same elongation andthickness reduction results in the absence of the cyclic plasticshearing strain. The tension applied, however, may desirably approach alevel at which the tension stress is just below the flow tension stressof the stock.

Those skilled in the art will understand that this invention centers toa large extent in a method concept since the procedures generallydescribed above may be carried out in a variety of different apparatusor machines in addition to the novel apparatus of my present inventiondescribed below. They will also understand that broadly and genericallydescribed the method of this invention comprises the steps of subjectingan elongated body to cyclic plastic strain, simultaneously subjectingthe body to tension stress insufficient of itself to produce plasticelongation of said body, and simultaneously also subjecting the saidbody to contact pressure sufiicient in combination with the cyclicplastic strain and the tension stress to reduce the thickness of thebody. More in detail, but still generically speaking, this methodinvolves subjecting successive portions of the length of the body to thecyclic plastic strain, the tension force and the contact pressuresimultaneously. Where metal strip employed in this method is ofthickness greater than 0.001 inch, the thickness reduction andelongation may be accomplished without increasing the width of the stripor body, and this is in sharp contrast to the action and results ofcertain conventional rolling operations. It will be understood that thismethod is not limited to use on strip thicker than 0.001 inch but thatit can be employed to obtain the foregoing new results where the stripthickness is of the order of 0.0001 or even thinner gauges.

Those skilled in the art will further understand that in one broadaspect the method of this invention is not mainly or only concerned withelongation, thinning or otherwise altering metal stock dimensions, buthas as a principal objective endowing the stock or work piece withspecial mechanical properties and novel combinations of such properties.Since the application of tension force to the stock is not necessary andmay even be detrimental in such operations, this form of the presentmethod may be generally described as comprising the steps of subjectingthe metal body to cyclic plastic strain in the range of from one percentto twenty percent or higher up to the point beyond which breakage wouldoccur and simultaneously subjecting the body to lateral forces topreserve body surfaces of the body against degradation due toplastically straining. In this aspect of the method, the metal stock maybe prepared in a particular manner for cyclic plastic strainingoperations and in this sense the method may be considered to include asa preliminary step or steps, one or another of several different typesof cold working or annealing operations. Further, in a preferredembodiment of this aspect of the invention, the cyclic plastic strainwill be produced by repeatedly bending and unbending the metal body,which is preferably in strip or sheet form, and the lateral forcespreserving the surface quality of the metal stock will be applied bymeans of contact rollers located at points of be i g and unbendi g s.will ub equently be desc ibed in detail. Also, in accordance with thisaspect of the present method, the dimensions of the work piece mayactually by significantly changed as desired with or without impartingto or endowing in the resulting product certain special mechanicalproperties or characteristics.

One of my principal discoveries constituting the basis of this newgeneral concept is that in the presence of a cyclic plastic strain ofsufficient magnitude, 2. stress and particularly a steady stress, evenof relatively low magnitude, can produce considerable deformation in abody of deformable material. More specifically, I have discovered thatif a metal body such as a metal sheet is subjected to contact rollpressure and to a tension force less than that necessary toindependently produce permanent elongation of the sheet and at the sametime the sheet is repeatedly bent and unbent or otherwise subjected tostresses resulting in cyclic plastic strains applied time and againtransversely of the sheet, the tension force and the contact pressurewill produce a drawing-out effect on the sheet, reducing its thicknessand increasing its length, while controlling its width and preserving oreven improving the quality of its surface. This operation thus iscarried out in such a manner that any tendency for the sheet to neckdown in thickness at any particular point is avoided or prevented withresulting substantially uniform reduction in stock thickness and theproduction of a sheet product of practically any desired thickness downto the thinnest kind of tape or foil, i.e., 0.001 inch or less. Unlike atypical rolling operation, the width of the sheet may not be increasedat any stage in the present process down to the point that the stockthickness is less than 0.001 inch, although its thickness may bedecreased to a limited and not desirable extent during such working.

The apparatus of this invention, broadly described, comprises a set ofthree rolls including a bend roll and two contact rolls spaced from eachother and opposed to the bend roll to bear against sheet or strip stockdisposed in contact around a portion of the circumference of the bendroll. The first and second contact rolls, like the bend roll, each havea working surface for engagement with stock to be thinned and theseveral rolls are arranged with respect to each other so that the fullwidth of such stock is engaged both by the bend roll and the contactrolls at the points at which the stock is bent and unbent in its travelin contact with the bend roll. The contact rolls are supported withtheir axes at a fixed distance from each other so that in one embodimentof the invention, the contact rolls may be moved together toward andaway from the bend roll which is on a fixed center, while in anotherembodiment of the invention, the bend roll may be moved toward and awayfrom the contact rolls which are on fixed centers. Further, while thevarious rolls may be on fixed centers, it is contemplated that they maybe adjusted in position relative to the axes of the other rolls toaccommodate varying operating circumstances.

In a preferred embodiment of this invention the bend roll will be afloating roll while the contact rolls will serve to back up or supportthe bend roll, being journalled in the rolling mill frame. By virtue ofthis arrangement very small diameter bend rolls can be employed withoutthe necessity for providing special and additional bend roll supportmeans. Then in a further modification of the apparatus of this inventionthe contact rolls or support rolls may both be driven, therebyeliminating the need to apply tension to pull the strip through themill. The upper limit to the amount of deformation imposed by apull-through system, which is governed by the maximum force that theoutcoming material can withstand, thus can be avoided. By still furtherinnovation, however, the capacity of the mills of this invention inrespect to the reductions that can be accomplished on each pass can besubstantially increased again. This modification consists generally inmaking the upstream supporting roll self-regulating in respect to itsdrive so that it ceases to drive the strip as effectively when theupstream tension of the strip falls below certain limits, the downstreamsupport roll being driven with a constant fixed rate at all times duringpassage of the strip through the mill. As a final alternative, thedownstream support roll may likewise be arranged to drive strip in atension-responsive manner.

The contact pressure in accordance with this invention is applied to thestock at the point where cyclic plastic strain is taking place. It isnot normally essential, however, that the stock be subjected to contactpressure at every plastic bending location. The nature of the stock andthe tendency for it to lose surface quality or to fracture, if of lowductility, under cyclic plastic strain processing will determine thenecessity for such surface treatment. Compared to the pressure appliedby rolls in heretofore conventional rolling operations, this surfacetreatment pressure is quite light and in fact can be insufficient ofitself and the applied tension to produce plastic deformation of thestock of the desired magnitude. Rolls are preferred for delivering orapplying this pressure to the stock but it will be understood by thoseskilled in the art that other means may satisfactorily be used. Diesegments or jaws which are not rolls and do not rotate are exemplary aswill subsequently be described.

Those skilled in the art will gain further and better understanding ofthis invention from the detailed description of several preferredembodiments of the method hereof, reference being had to the drawingsaccompanying and forming a part of this specification, in which FIG. 1is a perspective, somewhat diagrammatic view of apparatus for carryingout the method of this invention in one of its forms;

FIG. 2 is a fragmentary, longitudinal, sectional view of a part of theapparatus of FIG. 1, illustrating in exaggerated manner the action ofthe apparatus roller elements;

FIG. 3 is a fragmentary, side-elevational view of an apparatus forcarrying out the operations indicated in FIGS. 1 and 2, parts beingbroken away for purposes of clarity;

FIG. 4 is a fragmentary, sectional view taken on line 44 of FIG. 3;

FIG. 5 is a chart bearing curves illustrating the effect of thecombination of cyclic straining, contact roll pres sure and tensionstress applied simultaneously to sheet stock as will be described indetail below and also showing the necessity for contact pressure in thiscombination;

FIG. 6 is another chart bearing curves representing data showing theeffect of the process of the present invention as carried out in apreferred manner, as described in detail below;

FIG. 7 is a chart bearing curves illustrating a comparison between thecontact-bend-stretch rolling method of this invention and a heretoforeconventional tension rolling mill operation, roll force being plottedagainst percent reduction and important parameters being represented bythe fragmentary perspective sketch accompanying the chart;

FIG. 8 is a chart similar to FIG. 7 in which another heretoforeconventional type of rolling process is compared with the said presentinvention rolling method;

FIG. 9 is a chart similar to that of FIG. 7, comparing the said presentinvention method with still another prior conventional rollingoperation;

FIG. 10 is another chart bearing curves representing another comparisonbetween the present novel contactbend-stretch method and theconventional tension rolling operation concerned in FIG. 7, thicknessbeing plotted against percent reduction;

FIG. 11 is a diagrammatic sketch illustrating both lateralnon-uniformities in roll pressure and the lateral distribution oflongitudinal tenison stress in heretofore conventional tension rollingmethods;

FIG. 12 is a sketch like FIG. 11 illustrating both lateralnon-uniformities in roll pressure and lateral distribution 6 oflongitudinal tension stress distribution in a typicalcontact-bend-stretch operation of the present invention;

FIG. 13 is a schematic, side-elevational view of a rolling millembodying this invention in a preferred form;

FIG. 14 is an enlarged, fragmentary, side-elevational view of theapparatus of FIGURE 13 showing the bend roll in adjacent portions of thesupport rolls, strip stock in process being disposed around the bendroll and in engagement with the supporting rolls;

FIG. 15 is a view similar to FIGURE 14 showing still another rollingmill apparatus of this invention;

FIG. 16 is a fragmentary, side-elevational view of another embodiment ofthe apparatus of this invention designed for the purpose of processingductile material Where little or no tension is applied to the stock inprocess;

FIGURE 17 is a view similar to FIG. 16 wherein two driven bending rollunits including floating contact roller pairs are provided after themanner of the apparatus of FIG. 1.

With reference to FIGS. 1, 2, 3 and 4, it is seen that apparatuscomprising of relatively few parts will implement the embodiment of themethod of this invention which involves contact-bend-stretch rolling.The roll elements of this apparatus and their arrangement with respectto each other are illustrated to best advantage in FIGS. 1 and 2, whilein FIGS. 3 and 4 the means for supporting these elements and forapplying tension to the sheet stock and adjusting the pressure betweencertain roller elements are illustrated. In this apparatus there are twosets of three rolls each, including in each instance a bending roll andtwo contact rolls with stock S disposed between the bending roll and thecontact rolls opposed thereto. Thus, as shown in FIG. 1, sheet stock Sto be processed in accordance with this invention is carried on a feedreel 10 and disposed through two sets of proc essing rolls and collectedon pick-up reel 12. Reels 10 and 12 may alternatively be regarded assupply or pickup rolls depending upon the direction of travel of thissheet stock through the apparatus at a given time. As indicated in FIGS.1 and 3, reels 10 and 12 are maintained in position at all times duringthe operation of the apparatus and tension force is applied to stock Sthrough the maintenance of differential torque or angular velocity ofthese reels to produce the thickness reduction results desired.

The cyclic plastic straining of the stock essential under the tensionload and contact pressures applied in accordance with this invention toproduce the desired elongation, is developed as the stock is passedbetween opposed rolls of each of the sets of three rolls. The actionproducing cyclic straining is best illustrated in FIG. 2. With stock Sunder tension and moving from right to left around bending roll 13, itis first bent as it passes between roll 13 and contact roll 14 then itis unbent or straightened as it passes between contact roll 15 andbending roll 13. Due to the arrangement of the rolls with respect toeach other, a high degree of bending leverage is obtained so thatcomparatively small forces will produce plastic deformation, or in otherwords, the bending and unbending action illustrated in FIG. 2. Bendingroll 13 is a fixed roll, while the contact rollers are floating.

The degree of reduction of the stock is a function of the strip tension,the amount of plastic strain produced in bending the strip over thebending roll, and the pressure or force between the contact roll in eachinstance and the bending roll. It is also a function of theinstantaneous yield stress of the material of which the stock iscomposed.

In the machine shown in FIG. 3, the two sets of contact and bendingrolls 13, 14 and 15, are arranged in the manner illustrated in FIG. 1,with the exception that bending rolls 13 are fixed in position, beingjournaled in the machine frame as shown in FIG. 4 and contact rollers 14and 15 are floating since they are journaled in a roller frame 17. Theroller frame is disposed between and connected by means of a pivot pin18 to a pair of spaced members constituting lever 19 whereby lever 19may be moved on its pivot 20 to adjust the force between contact rolls14 and 15 and bending roll 13 simply by loading lever 26.

A second set of rolls 13, 14 and 15, is similarly supported in operatingrelation to the machine frame and lever 19 so that the same action isobtained in this group of rolls as in the first group described justabove. Thus, here again, bending roll 13 is journaled in the bifurcatedframe 21 and contact rolls 14 and 15 are journaled in another rollerframe 17, which in turn is secured by means of another pivot pin 18 to aportion of lever 19 on the opposite side of pivot pin 20 from the pointof connection of the first roll yoke assembly described above.

In the operation of the FIG. 3 apparatus as indicated in FIG. 1, thestock is wound and unwound from reels 10 and 12, which also constantlysupply the necessary tension in the stock. The stock is fed over thefirst bending roll and under the second one, contact being made with thetwo sets of contact rolls at the points of bending and unbending. Thestock is progressively reduced by the unique action illustrated to bestadvantage in FIG. 2. Since, as stated above, the degree of reduction isa function of the instantaneous yield stress of the material, striptension, force or pressure of contact rolls and amount of cyclic plasticstrain or bending, the rate at which reduction is accomplished per passthrough the mill can readily be adjusted within limits by regulation oftension in the stock through adjustment of the reel torque or therelative angular velocity between the two reels, to set the forceapplied to pull the stock back and forth. The reduction rate may also beregulated through adjustment of the pressure between the contact rollersand their respective bending rolls. This adjustment may be made byloading lever 26 to cause it to move downwardly as viewed in FIG. 3.

The following illustrative, but not limiting, example of the method ofthis invention as carried out on this apparatus is offered by way offurther explanation of the essential features of the invention in termsof an actual specific application or use.

EXAMPLE 1 Metal strip stock having an initial thickness of 40 mils and awidth of 1 inch was threaded through the FIG. 3 mill having two one-inchdiameter bend rolls and contacting rolls of the same size. Thiscontinuous, reversibletype mill was operated, running the stock first inone direction almost its full length then in the other direction to thesame extent, the stock being wound and unwound on the reels at the twoends of the machine. The supply and collection reels were run toestablish the tensile forces desired in the strip. Relative speeds ofeach reel are adjustable over wide ranges for this purpose. Dead weightsapplied to the ends of lever 26 exerted a force between the contactingrollers and the bend rollers in accordance with predetermined desiredresults.

The strip stock was oxygen-free, high-conductivity copper in theas-received state and it was processed in the cold or room-temperaturecondition. The yield stress of this material normally would be about50,000 p.s.i.

In the chart of FIG. the results obtained in this operation and therepetitions of this operation with varying conditions of rolling arediagrammatically illustrated. Thus the data from which Curve A wasplotted were gathered during an operation in which there was no contactpressure applied in the course of bending and unbending the stockrepeatedly around one-inch diameter rolls as it was passed back andforth through the mill under 40,000 p.s.i. tension in the reduced end ofthe strip. This particular rolling test was conducted on the millsomewhat modified from that of FIG. 3 in not having contact rolls 13 and14. Progressive roughening of the surface of the stock became more andmore pronounced until cracks developed which produced final severing ofthe strip at the point marking the lower end of Curve A. Just prior tothe breakage of the stock, surface conditions were such that the productwould be unsuitable for any manufacturing process and thus the necessityof the contacting rolls in this new process is demonstrated.

The data from which Curve B was plotted were collected in'the course ofa rolling-operation differing only from the operation above described inthat the mill of FIG. 3 was employed and contact roll pressure of 200lbs. per inch (essentially line contact) was applied continuously byeach one-inch-diameter roll. It may be noted that the actual reductionof the stock was not greatly altered over that obtained without thecontacting force, but a surface of good quality was obtained in thesheet product although in the first stages it appeared to be ratherrough. The strip did not break in this test, but a point of diminishingreturn was reached, as indicated by the asymptotic form of Curve B. Whenplastic reverse bending strains became too small to warrant continuationof the process as a practical matter, the test was stopped at the lowerend point of Curve B.

The data represented by Curve C were collected in an operation the sameas the operation of Curve B except that the contact force was 400 lbs.per inch of roll contact. As Curve C indicates, fairly uniform reductionper pass of about 17% is achieved with decreasing stock thickness.

Curve D depicts data gathered in an operation the same as thatrepresented by Curve C except a one-half inch contact roller was used.

An increase of substantial proportions in the effectiveness or rate ofreduction of the mill is indicated, particularly when the strip or sheetstock becomes relatively thin. In other words, as long as the strip orsheet stock is relatively thick, there appears to be little effect ofthe smaller diameter roll over the larger diameter roller, at least whenthe level of tensile stress is comparatively low. In the range belowl0-mil thickness the small diameter contact roller plays a significantpart in reducing the strip more rapidly and this is shown to bestadvantage in FIG. 6.

The data illustrated by Curve E of FIG. 6 were collected where thetension stress was 40,000 p.s.i. in the stock and the contact rollpressure of 200 lbs. per inch was applied. One-inch diameter contactrolls were used in producing the data of Curve E, while one-half inchdiameter contact rolls were used in producing the data of Curve F.Thicknesses down to 3 mils have been produced in strip processed underthe conditions of Curve F and the surface quality of this thin foil ortape is uniformly of the highest grade just as it is in the case ofCurve E and Curves B, C, and D of FIG. 5 where contact rolls were alsoused.

In addition to the operation described in Example 1, thecontact-bend-stretch method of this invention has been actually appliedto other metals and to stock of initial widths up to 12 inches andinitial thickness up to 100 mils (0.100 inch). Accounts of theseoperations are set forth in the following, non-limiting examples.

EXAMPLE II By using the contact-bend-stretch strip mill apparatusillustrated in FIGS. 1 and 2 and described in detail above and equippedwith bend rolls 12 inches long and one inch in diameter a mild steelstrip of initial nominal size of 94-mils (.094 inch) thickness and12-inch width was reduced in thickness in eleven passes to 6.2 mils,while the width was reduced to only 11.33 inch. The initialcrosssectional area of the strip was 1.130 square inches while thecross-sectional area of the final strip product was 0.0703 square inch.In the first pass a reduction in area of 20.5 percent was achieved asthe thickness was reduced from 94 mils to mils and the width was heldconstant. Strip tension stress upstream Was 885 lbs. per

9 square inch and downstream it was 28,200 lbs. per square inch. Contactroll pressure upstream was 2900 lbs. per linear inch of contact anddownstream it was 2820 lbs. per inch. The foregoing data and othersignificant information developed in the course of the run are setoutposes Physical properties of this initial aluminum m the followmgtable strip, this final product, and another final product obtainedTable I by rolling this initial strip in accordance with presently NG REconventional practice to precisely the same final thickness, CBS ROLLICORD compared as follows: Rolling mill: 12" CBS strip mill Bend rollradius, Tb (in.): Material: Mild stee lstrip gi g ifii g InitialConventional Final Nominal size: .094 thick 1: 12 wide 7Yielgstreiigghzl Strip tension Contact roll Strip geometry ma 163 23131322, 209 stress (lbs/in?) pressure Area red. gfgg g g g 213 965 22, 100Pass fif gf i' %ongitudinal gig. 2g, 75g 5 200 ransverse 08 6, 050 Inout L125", Cont Thick a Zi percent Vickers Hardness N o. 27 54. 5 50 ""0""820 0943 33 205 2, 90 .2, .075 .9 3,210 3,190 .060 .715 20.5EXAMPLE-IV 33 32 32 3-2 2, ,7 7 1,850 1,835 .019 226 234) In stillanother operation like that described in Exi'ggg iggg "81g ample II,Type 302 stainless steel 100-mils thick and six 1:380 1:280 .0' i l.1323 inches wide was contact-bend-stretch rolled on a 12-inch 23 28 18I 1-, mill under the circumstances and with the results set out 1,0801,080 .0002 .0703 23.5 in Table Table 3' The surface of the strip stockwas initially good, this stock being obtained on the market under thecommer- 013s ROLLING RECORD cial designation annealed, hot-rolled,mild-steel band. B mu mm 12' CBS m The quality of the surface wasmaintained throughout g r5011 ag a lythe rolling operation and the finalproduct had a good gatterlllalz '11:Iype 302 Stainless Steel toexcellent quality. This initial mild steel strip material ,1 3, and8/18/60 and this final product made from the strip had the follow- Nomal size: .100 thick 1: 6' wide ing physical characteristics.

Strip tension Contact roll Strip geometry 40 stress (lbs/in?) pressureArea red. Initial Final Pass gpreeed- 3 p In Out Lbs.l Cont. Thick Crosspercent Yield strength: in. see. area Longitudinal 37, 756 92, 360 UmTratnsversegf1 38, 275 104, 640 099 595 irnaestren 22 18% 222 332 2 3:;888 ransverse -2 1,300 1,300 132088 '8 i'i 'Sii '3 i, 0 00 .260 17.EXAMPLE m 122,000 4,000 4,000 .036 .204 21.5 128,000 4,000 4,000 .0272.153 25.0 Dead soft 2-S aluminum strip 100 mils thick and12.00 g 4,inches wide was contact-bend-stretch rolled to 21 mils and 1221000 400400 1 5 a width of 11.5 inches, as described in Example II. The g g 1significant data gathered are set out in Table 2. 1081000 2:840 2:840'0112 10618 7 r Table 2 50 CBS ROLLING RECORD The initial surfacequality of this stainless steel strip ggi i g gg g g gg was good and wasmaintained throughout the rolling r Material: Dead soft 2% Al gtripoperation and the final product therefore would meet the Z8p3 surfacequality requirements for commercial use. Physi- Size: .100 thick 21: 12'wide cal properties of this final product and a product obtained byrolling the same initial stainless steel strip material Strip tensionContact 1.011 strip geometry by presently conventional practice were asfollows: stress (lbs/in?) pressure Area red. Pass f/preced- L10 0 t Th k0 mg In Out s. on ic ross ercen in. sec. area p Conventional Final .1001.200 Percent Reduction.

5,530 500 500 .087 1. 040 13.3 70 Yield strength: 10, 370 500 500 .070.830 20.2 Longitudinal 227,100 273, 400 1:1 ;598 50g 288 .22? 1%.: Transv erse 22 00 285, 00 1 ,10 50 nna e s reng 3 13 3; 32 22 23 388 svrs17: 400 0 500 021 24 20 21. 8 Vickers Hardness N o 486 560 10 Again, thequality of the surface of the aluminum strip stock was initially goodand was maintained in the rolling operation so that the surface qualityof the final product was satisfactory for all commercial pur 1 1 EXAMPLEv Using the contact-bend-stretch strip mill of FIG. 1 as described aboveand in carrying out an operation after the manner set forth in Example1, a commercial alloy known in the trade as Rene-41, which had beensolution annealed, was contact-bend-stretch rolled in accordance withthe method of this invention under the circumstances and with theresults recorded in Table 4.

Table 4 CBS ROLLING RECORD Rolling mill: 1" CBS strip mill Bend rollradius, r (in): Material: Ren 41-S0lution annealed Test No. 177

Date: 7/17/60 Strip tension Contact roll Strip geometry stress (lbs/in?)pressure Area red. Pass i/preceding pass, In Out Lbs./ Cont. Thick Crosspercent in. sec. area The final rolled product had surface quality atleast as good as that of the initial material and had physicalproperties comparing with the initial material and with In anotheroperation like that described in Examples I and V, annealed 3% percentsilicon-iron strip of initial thickness of mils and width of 1 inch wasrolled to a final thickness of 7.3 mils and 0.916 inch. In this case thecontact roll radius was A; inch whereas in all the prior rollingoperations the con-tact roll radius was A or /2 inch. The significantdata in this run are set out in Table 5.

Table 5 CBS ROLLING RECORD Rolling mill: 1" CBS strip mill Bend rollradius, n, (in.):

Contact roll radius, r 1 Material: Annealed 3 4% silicon 11011 Test N o.48 Date: 10/2/58 Strip tension Contact roll Strip geometry stress(lbs/in!) pressure Area red. Pass f/preceding pass, In Out Lbs] Cont.Thick Cross percent in. sec. area The surface characteristics of thisfinished product were at least equal to those of the intial stock.

EXAMPLE VII Again in an operation like that described in Examples I andIV commercial L-605 alloy was contact-bendstretch rolled from an initialthickness of 43.6 mils and an intial width of 0.5 inch to 26 mils and a.width of 0.462 inch, in an apparatus as described above, where inchradius contact rollers were employed in contrast to the A: inch rollers'of Example VI. Pertinent data on this operation are set out in Table 6.

Table 6 CBS ROLLING RECORD Rolling mill: 1 CBS strip mill Bend rollradius, n, (in): Contact roll radius, rs:

Material: L-605 alloy Test No. 28 Date: 6/15/58 Strip tension Contactroll Strip geometry stress (lbs/in?) pressure Area red. Pass f/precedingpass, In Out Lbs.l Cont. Thick Cross percent in. sec. area Strip surfacequality was maintained throughout this operation.

EXAMPLE VIII Again, using the 1 inch contact-bend-stretch strip mill ofFIG. 1, as described in Example 1, commercial Jet-alloy 1650 which hadbeen solution treated and wet blast cleaned wasrolled from an initialthickness of 40.5 mils to 13 mils and from an initial width of 0.508inch to the final width of 0.487 inch. The pertinent data concerningthis operation appear in Table 7.

Table 7 CBS ROLLING RECORD Rolling mill: 1 CBS strip mill Bend rollradius Tb (in.): V Material: Jet Alloy 1650-solution treated-wet blastcleaned Test No. 40 Date: 8/7/58 Strip tension Contact roll Stripgeometry stress (lbs/in?) pressure Area red. Pass i/preceding pass, InOut L bs./ Cont. Thick Cross percent 111. see. area Physical propertiesof the finished rolled product compared favorably with the initialmaterial and the surface was apparently improved by the rollingoperation.

As a further comparison of the novel rolling method of this inventionwith heretofore conventional rolling practice, annealed copper strip(OFHC) 12 inches wide and mils thick had the yield strength and ultimatestrength values at several stages of the two rolling operations as setout in Table 8.

As indicated hereinabove, one of the fundamental differences between thenovel contact-bend-stretch rolling process of this invention and therolling processes of the prior art, is the fact that in the presentinvention process, the roll force or roll contact pressure is small bycomparison to all prior art rolling methods. Thus roll force inaccordance with prior practice was always necessarily greater than theforce necessary of itself to produce plas tic deformation of the stock,but the roll force in accordance with this invention is considerablyless than that required to so produce plastic elongation. By virtue ofthis difference it is possible for the first time in accordance with thepresent invention to subject stock during rolling to a tension stresswhich is relatively much greater than that which can be used underotherwise similar conditions in accordance with prior art practices. Inaccordance with this invention, in fact, the maximum tension stress towhich the stock is subjected during roll may in some cases safely andvery advantageously be maintained at a level approaching 95 percent ofthe flow stress of the stock.

Also, as indicated above and as will hereinafter be described in moredetail, rates of reduction which are unique and heretofore unknown andunattainable in rolling operations can be achieved in the presentprocess under certain conditions. This advantage over the prior art isof special importance in certain ranges of initial stock thickness andin certain types of materials.

These diiferenoes from and distinctions over the prior art aregraphically illustrated in FIGS. 7 to 12 inclusive.

As the sketch accompanying the chart of FIG. 7 indicates, a wide strip Sis subjected to contact roll force P per inch of width by roll 14 ofradius R and is simultaneously subjected to a tensile stress TS as thestock is being plastically bent at the point of contact with roll 14around a bend roller neither the bend roller nor the bend in the stripbeing shown. The strip is of thickness t, Curve K of FIG. 7 thenrepresents a typical contact-bendstretch operation of this invention,while Curve L represents a typical commercial tension mill operation inwhich the rolls are not driven and the stock is moved through the millby tension force alone. Curve M reppresents a modification of thetension mill operation of Curve L wherein the tensile stress ismaintained at a limit substantially higher than practical level of theCurve L operation. In the Curve K operation, tensile stress TS mayadvantageously be maintained at a value approaching 95% of TFS whichrepresents the flow stress of the stock. In the operation of Curve M,the tensile stress TS is likewise maintained at a very high level, whilein the case of the Curve L operation, tensile stress is limited to alevel which is less than 50% of the TFS value of the stock.

The operations represented by the curves of FIG. 7 are all carried outunder conditions of a fixed radius R and a fixed stock thickness 1. Thepercent reduction per pass is indicated for various roll forces P Theintersection of Curves K and M represents the limit of ef' fectivenessof the contact-bend-stretch method of this invention, the percentreduction for which is given by the expression Further processing of thestock in the contact-bend-stretch mill thus will not differ in terms ofresults or in actual process details from the tension mill operationrepresented by Curve M, the contact-bend-stretch mill in effect becominga high-tension tension mill. To give this critical transition point avalue for the sake of providing an illustrative example, assume an R of/2 inch, and a t of inch. The dotted line paralleling the abscissa andpassing through this transition point then will represent 40% reduction.The intersection point of Curves K and M represents for Curve K thereduction obtained in a single mill pass while that for Curve Mrepresents the reduction obtained in four mill passes. Similarly Curve Lrepresents four mill passes.

Curves K and M are shown again on the charts of FIGS. 8 and 9 along withthe point of their intersection defined by the expression signifying thepercentage reduction in a single pass in accordance with the method ofthis invention and in four passes in accordance with the conventionaltension mill practice,

In FIG. 8 the method of the present invention and the tension millmethod of Curve M are compared with another conventional operation inwhich the rolls are driven but strip S is not subjected to significanttensile stress. Curve N illustrates the typical performance of thelatter type mill. From this chart it is seen then that it is notpossible in Curve N type of rolling operation to produce the Curve Kresults of the present invention method and, in fact, it is not possibleeven to achieve the results of the conventional tension mill representedby Curve M or even the results of the typical tension mill operationrepresented by Curve L of FIG. 7.

In FIG. 9 Curves P and R represent driven-roll tension rollingoperations in which, respectively, tensile stress TS closely approachesTFS, as in the Curve K method, and TS is maintained at less than 50% ofTFS, as in the Curve L operation. Curve P thus represents a nontypicaland wholly impractical operation in which the tensile stress in thestock is actually substantially greater even than that of thenon-typical Curve L tension mill operation wherein the rolls are idlersand thus do not contribute to maintaining the tension stress in thestrip constant through the mill. The Curve P operation accordinglyrepresents maximum performance hitherto obtainable in terms of reductionrate, but because of excessive breakage of strip this operation hasnever been regarded as an answer to the problem of increasing tensionrolling efficiency.

It will be understood by those skilled in the art that while all theseoperations are capable of producing the same total thickness reduction,the rate at which the reduction is accomplished varies and it is thisdifference which is illustrated by the curves of FIGS. 7, 8, and 9. Inaddition to this etficiency aspect these charts show that thecontact-bend-stretch method of this invention is capable of producingresults previously unattainable, through the use of any magnitude oftensile stress or roll force or any combination thereof.

To compare further the present invention method with the conventionaltension rolling process represented by Curve L of FIG. 7 and also toillustrate the role of contact pressure or roll force, strip thicknessis plotted against percent reduction in FIG. 10. Two families of threecurves each represent characteristic data for these two different kindsof operation wherein Strip tension is the same but roll forces of threedifferent magnitudes are applied for direct comparison of the twoprocedures. Actually, in this case one mill pass of this invention iscompared with four mill passes of the conventional Steckel process.Thus, Curve T represents a tension rolling operation in which arelatively low roll force is applied to the strip, Curve U represents anoperation which is the same except that the roll force is substantiallygreater and in the case of Curve V the difference consists again in themagnitude of the roll force which is still greater by a substantialamount. Curves W, X, and Y similarly represent contact-bend-stretchrolling operations of this invention wherein the roll forces correspond,respectively, to those in the cases of Curves T, U and V and the rollforce magnitude, in each instance of comparison are exactly the same.

The points of intersection of the curves have the significance of theCurve KCurve M intersection described above in reference to FIG. 7 andtherefore define the operating limit of the present invention method ineach case. This definition is in terms of a relationship between stripthickness and bending roll radius and stated mathematically is where, asbefore, I is the strip thickness and R is the roll radius expressed inthe same dimensional unit. The dotted line extensions of Curves V, W andX do not represent real data or values but are merely used to indicatethe symmetry of the roll force relationships in this present inventionprocess.

As is evident, again, from FIG. 10, the contact-bendstretch method isuniquely effective in certain ranges of strip thickness, assuming aconstant bend roll diameter. In other words, so long as plastic bendingof the strip occurs during the rolling operation, the rate of stripthickness reduction will be greater than that obtainable in a tensionrolling operation in which the strip tension and the roll force areidentical in the two operations. Curves X and U illustrate this fact andthe other curve pairs of FIG. 10 repeat the demonstration. Thus it isseen that where the initial thickness of the strip to be rolled is TI,as designated by the dotted line connecting the ends of Curves W and Tand intersecting the abscissa, a vastly greater thickness reduction rateis achieved by this invention method than by the tension mill operation.As the strip thickness is reduced, this rate differential between thetwo operations diminishes until finally at strip thickness TF, the twocurves intersect, signifying that plastic bending is no longer occurringand that the contact-bendstretch method has become simply a tension milloperation. By substituting a bending roll of somewhat smaller radius,however, the present invention method may be continued into stillthinner strip thickness ranges, as indicated by Curve Z.

In addition to enabling the foregoing striking new results, the methodof this invention permits the use of much greater tensile stress inrolling operations than has hitherto been possible. This means thatrolling effectiveness may be substantially increased over the bestpreviously known and means further that this may be done simply byincreasing the tensile force applied to the strip as it is rolled. Onthe other hand, no modification of the prior rolling apparatus wouldenable such a result because the problem of strip breakage underexcessive tension could not be solved.

To illustrate this tension problem graphically, two cases representing,respectively, conventional rolling practices and thecontact-bend-stretch method of this invention are shown in FIGS. 11 and12. In these views, strip S again is subjected to tension stress TS andto roll force P per unit width and in each instance the roll forcenon-uniformly applied across the width of the strip. This non-uniformitymay be due to a number of factors such as lateral variations in stripthickness, roll crown, roll bending and thermal distortion of the rolls.Roll force seriously aggravates the tension problem attributable to anyof these factors, as will be described, and consequently reducing thatforce materially in any rolling operation could hold an importantadvantage. This force has been minimized in accordance with thisinvention beyond anything heretofore known or believed possible by thoseskilled in the art.

The lateral non-uniformities in roll force are diagrammatically shown inFIGS. 11 and 12 by Curves AA and BB, respectively. Under the tensileforce T normally applied in the rolling operation, lateral distributionof tension stress in strip S is digrammatically represented in FIG. 11by Curve CC, while the flow stress of strip S is indicated by TFS andthe working tension stress is represented by TWS. The expression fortension applied to the strip in this FIG. 11 case then is T=TWS A, whereA is the cross-sectional area of stock S, the maximum tension stressrepresented by the TM line very closely approaching the TFS while theworking stress is considerably less than TFS, say 0.5 TFS.

In the case of FIG. 12, where tensile force T is the same as in FIG. 11,strip S is again illustrated at the point where a contact roll bearsagainst the strip as it is bent around a bend roller, the bend roller,however, not being shown, and also for purposes of clarity, the strip isshown unbent as in FIG. 11. Here again, the distribution of roll forceacross the strip is correlated with the distribution of longitudinaltensile stress across the strip in this new rolling process. Curve BBrepresents this roll force distribution, while Curve DD depicts thetensile stress distribution laterally of the strip. Again, TFSrepresents the flow stress of the stock, while TWS represents theworking tension stress during the rolling process and TM represents themaximum tension stress applied to the strip in this operation. From FIG.12, therefore, it is seen that while TM very closely approaches TFS asin FIG. 16, here TWS is much larger, approaching 0.95 TFS, resulting ingreater reductions.

In these FIG. 11 and FIG. 12 operations, identical strips are involvedand the tensile force and the roll force are the same in each case.Further, as the drawings show, Curves AA and BB are generally the sameand those skilled in the art will understand that the differences inmagnitude are due to the difference in roll forces in the two cases.

Curves CC and DD, however, are not the same shape nor do they depictproportional values because of the following relationship:

Curve CC=TFSAA Curve DD=TFSBB From these drawings, it will be understoodthat in a given case of equivalent reductions in a conventional mill ofthe prior art and in the new contact-bend-stretch method, the roll forceis significantly less in the latter, although the relative variation inroll force is the same in the two situations. Consequently, in theconventional operation, the lateral variation of longitudinal tensilestress will be significantly greater, which imposes the necessity forlimiting average tensile stress on the strip to values not exceedingabout one-half the flow stress of the strip, to prevent its breakage.Because these lateral variations in tension may be relatively muchsmaller in the present process of rolling, tension (TWS) much greaterthan that permitted in prior rolling processes can consistently andsafely be employed and substantially greater rolling effectivenessthereby can be realized.

The method described herein has been demonstrated to reduce effectivelythe thickness and increase the length of strip where the ratio of stripthickness to bending roll diameter is initially 0.10 and decreases withreduction in thickness to 0.001. Larger initial ratios as, for example,0.25 to as high as 0.5 in some instances with soft ductile metals suchas aluminum or copper will be generally satisfactory, depending on thesusceptibility to fracture of the material being rolled, and upon thepreference of the operator.

Similarly, the ratio of the contact roller radius to the bend rollradius is not restricted but may be widely varied. The radius of thebend roll must, however, be related to the thickness of the strip stockand the nature of this stock to cause plastic deformation (bending) ofthe stock during the rolling operation.

As a practical matter, the initial thickness of strip material shouldprobably not exceed three inches, and where the strip is of steel, itshould preferably not be more than one inch thick. Such strip may be hotrolled in accordance with this invention to a thickness of about 0.1inch, and then cold rolled to the final desired thickness in acontinuation of the present method.

In accordance with the method of this invention, new products ormaterials having new combinations of physical characteristics canreadily and consistently be produced. Thus, I have found that by runningcertain material through apparatus of this invention and eithercontact-bend-stretch rolling the material, or contact-bend rolling thematerial under certain special circumstances, unique mechanicalproperties can be imparted to it or produced in it. By way of example, amild steel strip (SAE-l8 Steel) was run back and forth repeatedlythrough the apparatus of FIGS. 1 and 2 while the strip temperature wasmaintained between 100 C. and 300 C. Strengthening of the strip occurredvery quickly until its yield stress approached 100,000 p.s.i. Then thecyclicaged strip was cooled to room temperature and again run repeatedlyback and forth through the apparatus and a progressive softening effectwas observed. In this step of the operation, the cyclic strains were ofthe order of from two percent to ten percent strain range. In othersimilar operations, strains as high as fourteen percent uniformelongation can be obtained through subsequent mechanical cycling ofcyclic-aged mild steel in strain range of four percent for ten cycles atroom temperature.

In still another special application of the contact-bend method of thisinvention the apparatus of FIGS. 1 and 2 was used to improve theproperties of low carbon sheet steel strip. While a substantial tensileforce may be employed in this operation and relatively high tensilestresses may be set up in the strip, such is not essential to thedesired results. In the actual operation the strip was not subjected totension and a unique strip product was obtained, the yield point of thismaterial actually being eliminated for a considerable length of time. Inthe first step in this operation the strip was annealed. Then it was runthrough the FIG. 1 mill so as to produce a plastic bending strain offrom one to eight percent. The contact load was only sufficient to avoidsurface marking associated with the yield point effect and was thereforeof the order of 1000 pounds per linear inch for the oneinch contactroll. The rolling operation was carried out at room temperature and wasfollowed by a straightening step.

In thus employing the cyclic bending action of this invention forinitial yield point suppression, strain aged strengthening and improvedductility, the properties uniquely varied through the thickness of thestrip material. Consequently, a strip can be produced which will notexhibit either an upper or lower yield point, sliplines or othercharacteristics of the strain-aging phenomenum. Further, a wide range ofstrength and ductility in mild steel can thus be obtained while keepingthe percent reduction in area substantially constant.

These novel strip products and others like them that have been producedthrough this new procedure exhibit stability up to temperatures abovewhere such material is of normal commercial interest. By way of example,a specimen of cyclic strain-aged, strain-softened material, produced inthis manner was heated and held at a temperature of 250 C. for one-halfhour. A subsequent tensile test of this strip indicated that it wasessentially identical in stress-strain characteristics to the samematerial not so heated. Such apparent resistance to strain aging mayhave important technological interest in many metal forming processeswhere strain aging and Luders band formation are a considerable problem.

Again, these unique materials and combinations of physical properties invarious materials produced or processed in accordance with thisinvention are attributable to the present novel contact-bend-stretch orcontactbend operations. The metal or material, in other words issubjected in these operations to entirely different combinations offorces from thosewhich it encounters in heretofore conventional rollingoperations. The manner in which the plastic deformation, typicallyelongation, is accomplished is wholly unlike any of the prior proceduresand the manner in which the material is caused to flow or deform inorder to accomplish this result is likewise believed to be new anddifferent. It is, in fact, believed that these new procedures andresults and the new materials which this invention affords owe theirexistence to the novel way in which the metal or material of the bodyundergoing deformation is caused to flow under the applied forces.

Apparatus for carrying out the novel process of this invention which isalternative to -the novel apparatus of FIGS. 1 and 2 but employs eitherthe contact-bendstretch or the contact-bend principle and involvescyclically and plastically bending sheet stock is shown in FIGS. 13-15.In the FIG. 13 apparatus strip S is disposed around two contact orsupporting rolls 65 and 66 which define between their working surfaces agap of width somewhat greater than twice the initial width of the strip.Strip S also is disposed around the bend roll 67 which is positionedwith its axis parallel to the axes of rolls 65 and 66 and is situated soas to substantially close the gap between the contact rolls. An upstreambridle roll 68 and a downstream bridle roll 69 serve to deliver strip tothe bending roll and contact roll assembly and to receive the striptherefrom and to maintain the strip under requisite tension bothupstream and downstream from bend roll 67. In this arrangementsupporting rolls 65 and 66 are on fixed centers being suitablyjournalled in a rolling mill frame RF, while bend roll 67 is a floatingelement and is maintained in position in the gap' between rolls 65 and66 by strip S as illustrated to best advantage in FIG. 14. As describedabove in reference to FIGS. 1 and 2, it may be feasible or desirable torun strip S back and forth repeatedly through the bending station ofthis FIG. 13 apparatus, or it may be preferred to run it through thisstation only once and to have a series of such stations arranged forreduction of the strip thickness in separate steps. In the latter case,contact rolls 65 and 66 will suitably be driven at a predeterminedperipheral velocity ratio to each other so that the assembly willaccommodate the elongation resulting from the contact-bend-stretchingaction occurring at roll 67.

In the apparatus of FIG. 15, rolls 65, 66 and 67 again comprise theworking part of the mill but in this case roll 66 is not directlydriven. Instead, a second floating roll 70 is provided between upstreambridle roll 68 and roll 66. By virtue of this arrangement very heavyreductions can be effected in the new apparatus without any tendency forbend roll 67 to be drawn too far into the gap between the rolls 65 and66 with resulting excestorque from bridle roll 68 to support roll 66. Inorder for such torque transmission to occur, it is necessary that therebe adequate tension in the strip in this region. Consequently, adecrease in upstream strip tension, which might lead to excessivereduction and strip fracture as stated above, results in decrease in thetorque transmitted to the strip by roll 66. In other words, torquetransmitted to the strip by roll 66 is in this way related to upstreamstrip tension so that bend roll 67 does not tend to be drawn into themill and the necessary control is maintained. Very heavy reductions upto fifty percent per pass in materials such as aluminum have beensuccessfully accomplished over protracted periods of operation of thisFIG. apparatus. Again, as in the FIG. 19 apparatus, a rolling mill frameRF is provided and rolls 65, 66, 6S and 69 are journalled in andsupported by this frame.

FIGURES 16 and 17 represent alternatives in some respects to theapparatus of FIGURES 1 and 2. However, the bend rolls of FIGS. 16 and 17are driven so that in the event that tensile force applied to strip S isto be essentially zero, the strip may nevertheless be moved through themill as rapidly as desired. This kind of operation is contemplated inaccordance with one or another of the contact-bend methods of thisinvention subsequently to be described in detail. Accordingly, in FIGS.16 and 17 bend rolls are represented by 95 and contact rolls are 96 and97, these being mounted as floating pairs for movement together relativeto the associated bend roll 95. Again, after the manner of FIG. 1, stripS is moved through the mill between bend roll 95 and the opposingcontact rolls 96 and 97 which apply a contact pressure to the strip atthe point of plastic bending and plastic unbending so as to preserve oreven to improve the original surface quality of the strip.

Those skilled in the art will understand that instead of using in thenovel apparatus of this invention bend rolls or contact rolls which areof uniform outside diameter, stepped rolls may be employed. Likewise,contact rolls or bend rolls of other working surface shapes may beemployed. However, the same principles and parameters relative to cyclicplastic bend, tension and contact loads apply as in the foregoingdetailed descriptions. By this means certain advantages may be achievedin rolling strip of uniform thickness and, in addition, lateralvariations in strip thickness can be developed or produced for a varietyof commercial applications.

To avoid possible lateral bending of the strip and tracking problems,the roll pattern should be symmetrical in respect to the center line ofthe strip. Since the rolling process of the present invention enhancesuniformity in longitudinal strain because of the cyclic plastic bendingaction as previously described, variations in strip thickness which maybe produced are a consequence of lateral flow. Accordingly, it would notbe expected that very pronounced lateral variations in strip thicknesscan be produced when the strip is very wide and very thin because ofsevere lateral constraints to flow.

It is contemplated that such shaped roll elements may be used toadvantage in the production of commutator segments, stator cores, bladeand bucket materials and the like.

To illustrate the use of such contoured roll elements, two of the fourcontact rolls 14 and 15 of FIG. 1 may be shaped so that they engagestrip S only in its center region, while the other two contact rolls ofthis mill engage the strip only at its edges. By virtue of thisarrangement, excessive edge contact pressure which causes aredistribution of longitudinal stress due to strip tension and resultsin enhancing the tension in the central region of the strip, is avoided.Consequently, the tendency of the strip to undergo severe transversechecking and deterioration and possibly premature fracture is overcomebecause excessive tension coupled with reverse bending without adequatecontact loading or roll force is prevented.

Those skilled in the art will understand that in general the presentmethod is applicable to any elongated bodies which are deformable in thesense that strip or sheet metal is deformable at room temperature.Accordingly, it is contemplated that the present novel method may beapplied to a wide variety of materials under a wide variety ofenvironmental conditions to consistently produce or obtain theadvantages stated above. Thus, for example, a body of a material whichis not deformable at room temperature may successfully be subjected tothis invention method at a temperature well below or well above roomtemperature, depending upon the relative plasticity or brittleness ofthe body at room temperature.

Having thus described this invention in such full, clear, concise andexact terms as to enable any person skilled in the art to which itpertains to make and use the same, and having set forth the best modecontemplated of carrying out this invention, I state that the subjectmatter which I regard as being my invention is particularly pointed outand distinctly claimed in What is claimed, it being understood thatequivalents or modifications of, or substitutions for, parts of thespecifically described embodiments of the invention may be made withoutdeparting from the scope of the invention as set forth in what isclaimed.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Apparatus for increasing the length and uniformly reducing thethickness of metal strip, sheet or foil stock which comprises a frame, afirst bending roll journaled in the frame, a first contact rollrotatably supported adjacent to the first bending roll for pressingengagement with the stock across its width as the stock first engagesthe said first bending roll, a second contact roll rotatably supportedadjacent to the first bending roll and positioned for pressingengagement with the stock across the width of the stock as the stockleaves the first bending roll, a second bending roll journaled in theframe in radial spaced relation to the first bending roll, a thirdcontact roll rotatably supported adjacent to the second bending roll forpressing engagement with the stock across its width as the stock firstengages the second bending roll, a fourth contact roll rotatablysupported adjacent to the second bending roll with its axissubstantially paralleling that of said second bending roll and locatedto press the stock against the second bending roll at the point wherethe stock is having engagement with the said second bending roll, meansincluding a lever movably supported by the frame and operably associatedwith the four contact rolls for simultaneously adjusting the portions ofthe contact rolls relative to the bending rolls to regulate the contactroll pressure applied to the stock, and means for running the stock backand forth around the bending rolls and maintaining the stock in tensionin its travel around and between the bending rolls.

2. Apparatus for increasing the length of strip stock while subjectingthe stock to tensile stress and to roll pressure which comprises a rollframe including journal means for rotatably supporting contact rolls onfixed centers, an upstream contact roll, a driven upstream bridle roll,and a driven downstream contact roll, said contact rolls being ofrelatively large diameter journalled in the roll frame on fixed centersand spaced apart to provide a gap, a floating undriven bend roll ofrelatively small diameter bearing against and being supported entirelyby the contact rolls and substantially closing the gap therebetween,said bend roll being of diameter greater than the minimum width of thegap between the contact rolls and being small enough to cause plasticbending of the stock, and the contact rolls being of diameter such thatthe stock is not plastically bent in being disposed around said contactrolls as said stock is run through the roll assembly of the apparatus,and means for driving the.

contact rolls at predetermined relative peripheral velocities to achievesaid tensile stress and move the stock through the roll assembly.

3. Apparatus for increasing the length of strip stock which comprises aroll frame structure including journal means for rotatably supportingcontact rolls on fixed centers, an undriven upstream contact roll, adriven downstream contact roll, said contact rolls being of relativelylarge diameter and disposed with their axes substantially parallel toeach other and spaced apart to provide a gap as long as the opposedworking surfaces of said rolls and of width greater than twice theinitial thickness of the stock, a floating bend roll of relatively smalldiameter disposed to substantially close the gap between the contactrolls, said bend roll being of diameter greater than the minimum widthof the gap between the contact rolls, and means for maintaining apredetermined peripheral velocity ratio between the said upstream anddownstream contact rolls.

4. Apparatus for increasing the length of strip stock by plasticallybending the stock While subjecting it to tensile stress and to rollpressure which comprises a roll frame including journal means forrotatably supporting contact rolls on fixed centers, an upstream contactroll, a driven upstream bridle roll, and a driven downstream contactroll, said contact rolls being of relatively large diameter andjournalled in the roll frame on fixed centers and with their axessubstantially parallel to each other and spaced apart to provide a gapas long as the opposed Working surfaces of said contact rolls and ofwidth permitting free passage of strip stock simultaneously in two directions through the gap, 9. floating undriven bend roll of relativelysmall diameter disposed to substantially close the gap between thecontact rolls and to engage a strip stock loop leading through thecontact roll gap and to grip strip stock loop leads against the contactrolls, said bend roll being of diameter greater than the minimum widthof the gap between the contact rolls and small enough to produce plasticbending of strip stock, and means for driving the upstream bridle rolland the downstream contact roll at predetermined peripheral velocitiesrelative to each other to achieve said tensile stress and move stripstock through the roll assembly.

5. The method of cold working a metal strip and thereby reducing thethickness and increasing the length of the strip which comprises thesteps of advancing the strip along a travel course and overcoming theyield point of successive portions of the strip by plastically bendingthe strip at a first bending location, simultaneously subjecting thesuccessive portions of the strip to tension stress and to compressionforce suflicient in combination with said plastic bending to reduce thethickness of the strip without degrading the surface quality of thestrip, then transferring the resulting bent portions to a firstunbending location spaced from the first bending location, thenadvancing the said bent portions of the strip through the firstunbending location and overcoming the yield point of successive bentportions by plastically unbending said bent portions, simultaneouslysubjecting the successive bent portions of the strip to tension stressand to compressive force sufiicient in combination with said plasticunbending to reduce the thickness of the strip without degrading thesurface quality of the strip, then transferring the resulting successiveplastically unbent portions of the strip through a distance at least aslong as the distance between the first bending location aud the firstunbending location and thereby bringing the said unbent portions of thestrip to a second bending location spaced from the first unbendinglocation, then advancing the said unbent cold-worked portions of thestrip through the second bending location and overcoming the yield pointof successive cold-worked portions of the strip by plastically rebendingthe strip, simultaneously subjecting the strip to tension stress andcompression force sufiicient in combination with the plastic bendingfurther to reduce the thickness of the strip Without degrading the stripsurface, then transferring the resulting plastically rebent coldworkedportions of the strip farther along the travel course to a secondunbending location spaced from the second bending location, thenadvancing the said rebent portions of the strip through the secondunbending location and overcoming the yield point of successive rebentportions of the strip by plastically unbending the said rebent portions,simultaneously subjecting the strip to tension stress and compressionforce sufficient in combination with plastic unbending to reduce stillfurther the thickness of the strip without degrading the strip surface,and repeating the foregoing sequence of bending and transferring andunbending steps until the strip is of final desired thickness.

References Cited by the Examiner UNITED STATES PATENTS 1,347,917 7/1920Sheperdson -60 1,861,525 6/1932 Edwards 80-35 2,004,596 6/1935 Biggert153-54 2,067,192 1/1937 Hudson 80-60 2,163,504 6/1939 Thomas 153-542,166,418 7/1939 McBain 80-60 2,291,361 7/ 1942 Walsh 80-60 2,332,79610/1943 Hume 80-32 2,370,895 3/1945 Wean 80-60 2,432,828 12/1947 Stone153-85 2,479,353 8/1949 Hansell 153-64 2,526,296 10/ 1950 Stone 80-352,742,949 4/1956 Nilsson 153-90 2,801,669 8/1957 Lermont 153-642,857,655 10/1958 Greenberger 153-93 2,878,553 3/1959 Hirsch 29-1803,126,303 3/1964 Armitage 148-36 CHARLES W. LANHAM, Primary Examiner.

LEON PEAR, WILLIAM J. STEPHENSON, Examiners.

1. APPARATUS FOR INCREASING THE LENGTH AND UNIFORMLY REDUCING THETHICKNESS OF METAL STRIP, SHEET OR FOIL STOCK WHICH COMPRISES A FRAME, AFIRST BENDING ROLL JOURNALED IN THE FRAME, A FIRST CONTACT ROLLROTATABLY SUPPORTED ADJACENT TO THE FIRST BENDING ROLL FOR PRESSINGENGAGEMENT WITH THE STOCK ACROSS ITS WIDTH AS THE STOCK FIRST ENGAGESTHE SAID FIRST BENDING ROLL, A SECOND CONTACT ROLL ROTATABLY SUPPORTEDADJACENT TO THE FIRST BENDING ROLL AND POSITIONED FOR PRESSINGENGAGEMENT WITH THE STOCK ACROSS THE WIDTH OF THE STOCK AS THE STOCKLEAVES THE FIRST BENDING ROLL, A SECOND BENDING ROLL JOURNALED IN THEFRAME IN RADIAL SPACED RELATION TO THE FIRST BENDING ROLL, A THIRDCONTACT ROLL ROTATABLY SUPPORTED ADJACENT TO THE SECOND BENDING ROLL FORPRESSING ENGAGEMENT WITH THE STOCK ACROSS ITS WIDTH AS THE STOCK FIRSTENGAGES THE SECOND BENDING ROLL, A FOURTH CONTACT ROLL ROTATABLYSUPPORTED ADJACENT TO THE SECOND BENDING ROLL WITH ITS AXISSUBSTANTIALLY PARALLELING THAT OF SAID SECOND BENDING ROLL AND LOCATEDTO PRESS THE STOCK AGAINST THE SECOND BENDING ROLL AT THE POINT WHERETHE STOCK IS HAVING ENGAGEMENT WITH THE SAID SECOND BENDING ROLL, MEANSINCLUDING A LEVER MOVABLY SUPPORTED BY THE FRAME AND OPERABLY ASSOCIATEDWITH THE FOUR CONTACT ROLLS FOR SIMULTANEOUSLY ADJUSTING THE PORTIONS OFTHE CONTACT ROLLS RELATIVE TO THE BENDING ROLLS TO REGULATE THE CONTACTROLL PRESSURE APPLIED TO THE STOCK, AND MEANS FOR RUNNING THE STOCK BACKAND FORTH AROUND THE BENDING ROLLS AND MAINTAINING THE STOCK IN TENSIONIN ITS TRAVEL AROUND THE BETWEEN THE BENDING ROLLS.
 5. THE METHOD OFCOLD WORKING A METALK STRIP AND THEREBY REDUCING THE THICKNESS ANDINCREASING THE LENGTH OF THE STRIP WHICH COMPRISES THE STEPS OFADVANCING THE STRIP ALONG A TRAVEL COURSE AND OVERCOMING THE YIELD POINTOF SUCCESSIVE PORTIONS OF THE STRIP BY PLASTICALLY BENDING THE STRIP ATA FIRST BENDING LOCATION, SIMULTANEOUSLY SUBJECTING THE SUCCESSIVEPORTIONS OF THE STRIP TO TENSION STRESS AND TO COMPRESSION FORCESUFFICIENT IN COMBINATION WITH SAID PLASTIC BENDING TO REDUCE THETHICKNESS OF THE STRIP